Different types of devices, which can be opened, are used as protection from view, for screening of sun rays and, sometimes, as reinforced burglary protection. Apart from the main type windows or doorshutters, there is another main type where screening devices are pulled or rolled down in front of the opening in the window or door, respectively, and which distinguishes itself from curtains and drapes by being, in general, of a stronger material than textile and arranged with a more technically emphasised closing mechanism. Such devices are generally called Venetian blinds or roller blinds, which last designation will be used here.
Many types of roller blinds have the only task of functioning as protection from view and sunscreens, and do not need to be of any more robust construction. Certain types, on the other hand, are intended to also function as reinforced burglary protection or, for some types, only as such. As an example, ribbed blinds can be mentioned, which are generally found in areas with a strong solar radiation and which, because the closure device is made of wood or steel ribs running in rails, cause a certain amount of hindrance during an attempted burglary. They do, however, form heavy and relatively bulky structures and require relatively large adaptations of the building construction for their installation. Another increasingly common type is represented by grid constructions, which can be pulled or rolled in front of the opening in a building. They are mainly used in public environments, such as for shop windows, entrances to shops or institutions, for subways etc. These constructions are relatively bulky too and are also expensive to manufacture because they consist of a great number of parts which have to be attached to each other in a flexible manner.